Performa 640CD DOS Compatible crashing with BUS ERROR on boot

[MrFahrenheit]

I picked up a Performa 640CD with the infamous DOS Compatible card inside. I have verified it's there and everything looks good.

When I first booted up the machine, the OS would freeze. I decided to boot off an external disk, and copy the contents over and reformat.

Doing so, resulted in lots of lag on some files. Seems there are some corrupt files on the boot disk. No problem.

I formatted it while booted in Mac OS 7.6.1 and installed a fresh copy of Mac OS 7.5.5. Upon reboot, when it gets to PC Setup control panel, a system bomb appears with BUS Error as the message.

What would cause this, and how can I go about verifying the DOS card?

 

[Phipli]

I picked up a Performa 640CD with the infamous DOS Compatible card inside. I have verified it's there and everything looks good.

When I first booted up the machine, the OS would freeze. I decided to boot off an external disk, and copy the contents over and reformat.

Doing so, resulted in lots of lag on some files. Seems there are some corrupt files on the boot disk. No problem.

I formatted it while booted in Mac OS 7.6.1 and installed a fresh copy of Mac OS 7.5.5. Upon reboot, when it gets to PC Setup control panel, a system bomb appears with BUS Error as the message.

What would cause this, and how can I go about verifying the DOS card?

Start by unplugging the IDE disk and boot from a known good SCSI drive on the external port. If it still plays up, slide the logic board out and reseat the 486, 040 and the DOS card entirely. They seem particularly prone to bad contact. Re paste the 486 while you're at it.

And reseat the RAM

 

[volvo242gt]

And, if all that doesn't help, start looking for extension conflicts. Possible that stuff like the CFM-68K Runtime Enabler might not be playing nice with the PC Setup control panel.

 

[MrFahrenheit]

Removed all RAM. Replaced system RAM with a single known good simm. No effect.

Removed all extensions and only had PC Setup control panel. Still crashes with Bus Error.

I’ll have to investigate the rest when I have the patience to deal with it.

 

[MrFahrenheit]

When all else fails, keep trying.

I went back to my clean install of 7.6.1. I tracked down the DOS Compatibility software install for 7.6.1 that was on one of my tools disks, and presto! No more bus error!

 

[MrFahrenheit]

So for some reason the Mac OS 7.5.5 with PC Setup 1.0.1 crashes on boot, but Mac OS 7.6.1 with PC Setup 1.0.6 works just fine.

View attachment IMG_9386.mov

 

[volvo242gt]

That's weird. That said, since the Quadra 630 (and its derivatives) seems to not have 24-bit addressing mode available, there's no real reason to run it on anything older than 7.6 anyway.

 

[MrFahrenheit]

Looks like I have an undocumented version of the PC Setup control panel software.

I've uploaded it to the Macintosh Garden here: https://macintoshgarden.org/apps/ap...f2-100mb-pc-drive-image-dos-622-pre-installed